Trademarks: IBM® may be a registered trademark of International Business Machines Corporation, Armonk, N.Y., U.S.A. S/390®, z900 and z990 and other product names are registered trademarks or product names of International Business Machines Corporation or other companies.
Before our invention IBM has created through the work of many highly talented engineers beginning with machines known as the IBM® System 360 in the 1960s to the present, a special architecture which, because of its essential nature to a computing system, became known as “the mainframe” whose principles of operation state the architecture of the machine by describing the instructions which may be executed upon the “mainframe” implementation of the instructions which had been invented by IBM inventors and adopted, because of their significant contribution to improving the state of the computing machine represented by “the mainframe”, as significant contributions by inclusion in IBM's Principles of Operation as stated over the years. The Eighth Edition of the IBM® z/Architecture® Principles of Operation which was published February, 2009 has become the standard published reference as SA22-7832-07 and are incorporated in IBM's z9® mainframe servers. The IBM Z/Architecture® Principles of Operation, Publication SA22-7832-07 is incorporated by reference in its entirety herein.
Referring to FIG. 1A, representative components of a prior art Host Computer system 50 are portrayed. Other arrangements of components may also be employed in a computer system, which are well known in the art. The representative Host Computer 50 comprises one or more CPUs 1 in communication with main store (Computer Memory 2) as well as I/O interfaces to storage devices 11 and networks 10 for communicating with other computers or SANs and the like. The CPU 1 is compliant with an architecture having an architected instruction set and architected functionality. The CPU 1 may have Dynamic Address Translation (DAT) 3 for transforming program addresses (virtual addresses) into real address of memory. A DAT typically includes a Translation Lookaside Buffer (TLB) 7 for caching translations so that later accesses to the block of computer memory 2 do not require the delay of address translation. Typically a cache 9 may be employed between Computer Memory 2 and the Processor 1. The cache 9 may be hierarchical having a large cache available to more than one CPU and smaller, faster (lower level) caches between the large cache and each CPU. In some implementations the lower level caches are split to provide separate low level caches for instruction fetching and data accesses. In an embodiment, an instruction may be fetched from memory 2 by an instruction fetch unit 4 via a cache 9. The instruction may be decoded in an instruction decode unit (6) and dispatched (with other instructions in some embodiments) to instruction execution units 8. Typically several execution units 8 are employed, for example an arithmetic execution unit, a floating point execution unit and a branch instruction execution unit. The instruction may be executed by the execution unit, accessing operands from instruction specified registers or memory as needed. If an operand is to be accessed (loaded or stored) from memory 2, a load store unit 5 typically handles the access under control of the instruction being executed. Instructions may be executed in hardware circuits or in internal microcode (firmware) or by a combination of both.
U.S. Pat. No. 5,560,013 “METHOD OF USING A TARGET PROCESSOR TO EXECUTE PROGRAMS OF A SOURCE ARCHITECTURE” to Scalzi et al., filed Dec. 6, 1994, assigned to IBM, incorporated by reference herein teaches a method of utilizing large virtual addressing in a target computer to implement an instruction set translator (1ST) for dynamically translating the machine language instructions of an alien source computer into a set of functionally equivalent target computer machine language instructions, providing in the target machine, an execution environment for source machine operating systems, application subsystems, and applications. The target system provides a unique pointer table in target virtual address space that connects each source program instruction in the multiple source virtual address spaces to a target instruction translation which emulates the function of that source instruction in the target system. The target system efficiently stores the translated executable source programs by actually storing only one copy of any source program, regardless of the number of source address spaces in which the source program exists. The target system efficiently manages dynamic changes in the source machine storage, accommodating the nature of a preemptive, multitasking source operating system. The target system preserves the security and data integrity for the source programs on a par with their security and data integrity obtainable when executing in source processors (i.e. having the source architecture as their native architecture). The target computer execution maintains source-architected logical separations between programs and data executing in different source address spaces—-without a need for the target system to be aware of the source virtual address spaces.
“Dynamic Native Optimization of Interpreters” published 2000 by Hewlett-Packard Labs 1 Main St. Cambridge, Ma 02142 from the world wide web incorporated herein by reference teaches “There is a long history of approaches to removing interpretive overhead from programming language implementations. In practice, what often happens is that, once an interpreted language becomes popular, pressure builds to improve performance until eventually a project is undertaken to implement a native Just In Time (JIT) compiler for the language. Implementing a JIT is usually a large effort, affects a significant part of the existing language implementation, and adds a significant amount of code and complexity to the overall code base.”
In FIG. 1B, an example of a prior art emulated Host Computer system 21 may be provided that emulates a Host computer system 50 of a Host architecture. In the emulated Host Computer system 21, the Host processor (CPU) 1 may be an emulated Host processor (or virtual Host processor) and comprises an emulation processor 27 having a different native instruction set architecture than that of the processor 1 of the Host Computer 50. The emulated Host Computer system 21 has memory 22 accessible to the emulation processor 27. In the example embodiment, the Memory 27 may be partitioned into a Host Computer Memory 2 portion and an Emulation Routines 23 portion. The Host Computer Memory 2 may be available to programs of the emulated Host Computer 21 according to Host Computer Architecture. The emulation Processor 27 executes native instructions of an architected instruction set of an architecture other than that of the emulated processor 1, the native instructions obtained from Emulation Routines memory 23, and may access a Host instruction for execution from a program in Host Computer Memory 2 by employing one or more instruction(s) obtained in a Sequence & Access/Decode routine which may decode the Host instruction(s) accessed to determine a native instruction execution routine for emulating the function of the Host instruction accessed. Other facilities that are defined for the Host Computer System 50 architecture may be emulated by Architected Facilities Routines, including such facilities as General Purpose Registers, Control Registers, Dynamic Address Translation and I/O Subsystem support and processor cache for example. The Emulation Routines may also take advantage of function available in the emulation Processor 27 (such as general registers and dynamic translation of virtual addresses) to improve performance of the Emulation Routines. Special Hardware and Off-Load Engines may also be provided to assist the processor 27 in emulating the function of the Host Computer 50.
In a mainframe, architected machine instructions are used by programmers, usually today “C” programmers often by way of a compiler application. These instructions stored in the storage medium may be executed natively in a z/Architecture IBM Server, or alternatively in machines executing other architectures. They can be emulated in the existing and in future IBM mainframe servers and on other machines of IBM (e.g. pSeries® Servers and xSeries® Servers). They can be executed in machines running Linux on a wide variety of machines using hardware manufactured by IBM®, Intel®, AMD™, Sun Microsystems and others. Besides execution on that hardware under a Z/Architecture®, Linux can be used as well as machines which use emulation by Hercules, UMX, FSI (Fundamental Software, Inc) or Platform Solutions, Inc. (PSI), where generally execution may be in an emulation mode. In emulation mode, emulation software may be executed by a native processor to emulate the architecture of an emulated processor.
The native processor 27 typically executes emulation software 23 comprising either firmware or a native operating system to perform emulation of the emulated processor. The emulation software 23 may be responsible for fetching and executing instructions of the emulated processor architecture. The emulation software 23 maintains an emulated program counter to keep track of instruction boundaries. The emulation software 23 may fetch one or more emulated machine instructions at a time and convert the one or more emulated machine instructions to a corresponding group of native machine instructions for execution by the native processor 27. These converted instructions may be cached such that a faster conversion can be accomplished. Not withstanding, the emulation software must maintain the architecture rules of the emulated processor architecture so as to assure operating systems and applications written for the emulated processor operate correctly. Furthermore the emulation software must provide resources identified by the emulated processor 1 architecture including, but not limited to control registers, general purpose registers, floating point registers, dynamic address translation function including segment tables and page tables for example, interrupt mechanisms, context switch mechanisms, Time of Day (TOD) clocks and architected interfaces to I/O subsystems such that an operating system or an application program designed to run on the emulated processor, can be run on the native processor having the emulation software.
A specific instruction being emulated may be decoded, and a subroutine called to perform the function of the individual instruction. An emulation software function 23 emulating a function of an emulated processor 1 may be implemented, for example, in a “C” subroutine or driver, or some other method of providing a driver for the specific hardware as will be within the skill of those in the art after understanding the description of the preferred embodiment. Various software and hardware emulation patents including, but not limited to U.S. Pat. No. 5,551,013 for a “MULTIPROCESSOR FOR HARDWARE EMULATION” of Beausoleil et al.; and U.S. Pat. No. 6,009,261 “PREPROCESSING OF STORED TARGET ROUTINES FOR EMULATING INCOMPATIBLE INSTRUCTIONS ON A TARGET PROCESSOR” of Scalzi et al; and U.S. Pat. No. 5,574,873 “DECODING GUEST INSTRUCTION TO DIRECTLY ACCESS EMULATION ROUTINES THAT EMULATE THE GUEST INSTRUCTIONS” of Davidian et al; and U.S. Pat. No. 6,308,255 “SYMMETRICAL MULTIPROCESSING BUS AND CHIPSET USED FOR COPROCESSOR SUPPORT ALLOWING NON-NATIVE CODE TO RUN IN A SYSTEM” of Gorishek et al; and U.S. Pat. No. 6,463,582 “DYNAMIC OPTIMIZING OBJECT CODE TRANSLATOR FOR ARCHITECTURE EMULATION AND DYNAMIC OPTIMIZING OBJECT CODE TRANSLATION METHOD” of Lethin et al; and U.S. Pat. No. 5,790,825 “METHOD FOR EMULATING GUEST INSTRUCTIONS ON A HOST COMPUTER THROUGH DYNAMIC RECOMPILATION OF HOST INSTRUCTIONS” of Eric Traut, each of which are incorporated by reference herein, and many others, illustrate the a variety of known ways to achieve emulation of an instruction format architected for a different machine for a target machine available to those skilled in the art, as well as those commercial software techniques used by those referenced above.
U.S. Pat. No. 5,953,520 “Address Translation Buffer for Data Processing System Emulation Mode”, (Mallick) assigned to IBM, Filed Sep. 22, 1997 and incorporated herein by reference, teaches a processor and method of operating a processor which has a native instruction set and emulates instructions in a guest instruction set are described. According to the method, a series of guest instructions from the guest instruction set are stored in memory. The series includes a guest memory access instruction that indicates a guest logical address in guest address space. For each guest instruction in the series, a semantic routine of native instructions from the native instruction set may be stored in memory. The semantic routines, which utilize native addresses in native address space, can be executed in order to emulate the guest instructions. In response to receipt of the guest memory access instruction for emulation, the guest logical address may be translated into a guest real address, which may be thereafter translated into a native physical address. A semantic routine that emulates the guest memory access instruction may be then executed utilizing the native physical address.